Canalisation and Selection

Rendel, J M

doi:10.1016/b978-0-12-688850-8.50014-3

Cited by 53 publications

(61 citation statements)

References 54 publications

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“…An alternative method to detect variant effects is to select away the phenotypic extremes by breeding individuals that have the population's median phenotype ( Figure S1). Other groups have successfully practiced median-selection regimes upon sc populations, and indeed, selection for a median or average phenotype causes a reduction in the frequency of nonaverage phenotypes (Rendel 1959(Rendel , 1967). An advantage to this approach is that one can simultaneously compare the below-median with above-median response rates during median-selection.…”

Section: Mir-9a Asymmetrically Affects Response To Medianselectionmentioning

confidence: 99%

Differential Masking of Natural Genetic Variation by miR-9a inDrosophila

2015

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Genetic variation is prevalent among individuals of the same species and yet the potential effects of genetic variation on developmental outcomes are frequently suppressed. Understanding the mechanisms that are responsible for this suppression is an important goal. Previously, we found that the microRNA miR-9a mitigates the impact of natural genetic variants that promote the development of scutellar bristles in adult Drosophila. Here we find that miR-9a does not affect the impact of genetic variants that inhibit the development of scutellar bristles. We show this using both directional and stabilizing selection in the laboratory. This specificity of action suggests that miR-9a does not interact with all functional classes of developmental genetic variants affecting sensory organ development. We also investigate the impact of miR-9a on a fitness trait, which is adult viability. At elevated physiological temperatures, miR-9a contributes to viability through masking genetic variants that hinder adult viability. We conclude that miR-9a activity in different developmental networks contributes to suppression of natural variants from perturbing development. KEYWORDS Drosophila; miRNA; heritability; sensory organs; development O RGANISMS are subject to conditions of genetic variation, and yet their morphological development is often robust to such challenges. Hence, developmental outcomes are rendered uniform even in the face of variable conditions of existence. The relationship between this developmental robustness and phenotypic variation in natural populations has long been remarked upon, and Waddington (1942) coined the word canalization to describe the process. As development becomes more robust, less phenotypic variation is observed among individuals in a population (Scharloo 1991;de Visser et al. 2003;Siegal and Leu 2014). This has implications not only for the relationship between genotype and phenotype, but also for evolution (Gibson and Wagner 2000;Gibson and Dworkin 2004;Wagner 2012). In one sense, robustness inhibits evolvability since it suppresses the phenotypic variation that selection acts upon. However, when a phenotype is robust to the effects of mutations, then genetic variation can potentially accumulate in a neutral state. This might permit a broad set of connected genotypes to express the same phenotype (Wagner 2012). Later, if canalization is impaired, the effects of the previously cryptic genetic variation are revealed as phenotypic variability. These can be subject to selection, thus enhancing evolvability.Morphological variation is a consequence of variable development between individuals. Development, in turn, is the complex outcome of dynamic interactions between regulatory molecules. Developmental dynamics have been successfully simulated by biochemical reaction network models, which vary in size, topology, and circuit composition and depend upon the specific developmental process, tissue type, and species (Kitano 2004;Stathopoulos and Levine 2005;Wunderlich and DePace 2011). Studie...

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Section: Mir-9a Asymmetrically Affects Response To Medianselectionmentioning

confidence: 99%

Differential Masking of Natural Genetic Variation by miR-9a inDrosophila

2015

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“…One argument is that traits with a high impact on fitness are expected to be canalized, i.e. under the control of mechanisms that constrain the trait to be closer to the optimum (Rendel, 1967). Canalization can be against environmental perturbations (e.g.…”

Section: (Iii) Rele Ance For the E Olution Of Sexmentioning

confidence: 99%

Synergistic epistasis between loci affecting fitness: evidence in plants and fungi

Visser

Hoekstra

1998

Genet. Res.

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SummaryInformation on the nature of epistasis between alleles affecting fitness is hardly available, but relevant for, among other issues, our understanding of the evolution of sex and recombination. Evidence of synergistic epistasis between deleterious mutations is support for the Mutational Deterministic hypothesis of the evolution of sex, while finding antagonistic epistasis between beneficial alleles would support the Environmental Deterministic hypotheses. Both types of epistasis are expected to cause negatively skewed fitness distributions of full-sib offspring from a sexual cross. Here, we have studied the form of the distribution of a variety of quantitative characters related to fitness by searching the literature. The fitness traits encountered include the mycelial growth rate in fungi, and earliness, resistance against pathogens, seed number, and pollen fitness in plants. Fitness-related traits in plants show almost exclusively negative skewness, while the results for fungal species are more ambiguous. Possible sources of negative skewness other than epistasis, such as recessiveness of deleterious alleles or a negatively skewed error variance, were tested and found to be unimportant. We argue that these results suggest the existence of synergistic epistasis between deleterious alleles or antagonistic epistasis between beneficial alleles in plants, which is general support for the currently popular hypotheses of sex and recombination, but does not distinguish between them.

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“…see Rendel 1967;Sheldon and Milton 1972), the scutellar bristle data were transformed to the probit scale to aid analysis of changes in canalization and dominance. are not shown for the relaxed lines in Fig.…”

Section: Line A5mentioning

confidence: 99%

“…Sheldon (1968) following Rendel et al (1965) and Rendel (1967Rendel ( , 1968Rendel ( , 1969 had held the hypothesis that canalization at four bristles in wild type is accomplished by genetic regulation of the scute locus and that selection for high bristle number merely changed the minor gene background without affecting the canalization genotype. In contrast to this, Sheldon and Milton (1972) interpreted * Part II, Genetics, 1972, 71, 567-95. t Formerly Milton.…”

Section: Introductionmentioning

confidence: 99%

Studies on the Scutellar Bristles of Drosophila Melanogaster ID. Long-Term Selection for High Bristle Number in Three further Lines Derived From the Oregon-RC Strain, Correlated Responses in Abdominal Bristles, lUld Changes in Regulation of the Scute Locu

Sheldon¹,

Evanst²

1981

Aust. Jnl. Of Bio. Sci.

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Results of selection over 135 generations for high scutellar bristle number in three further lines derived from Oregon-RC complement those on the four lines reported previously (Sheldon and Milton 1972). All lines differed widely in pattern of scutellar response, correlated response in abdominal and posterior central scutellar bristles, sex differences, and behaviour on relaxing selection, though the selection limits reached in the present three lines were lower than in the previous lines.The early scutellar response supports the conclusion in the previous paper that early selection was mainly for poor regulation of the scute locus at the canalization level of control, since the probit span of the four-bristle class decreased as the mean scutellar number increased in the selection lines, and increased in the relaxed lines as the mean scutellar score decreased.Introduction of the set allele into the selection lines confirmed the earlier findings that the selected background increased scutellar bristles in set to a much lesser extent than in sc+ flies, and that considerable interaction of set and sc+ with selected background occurred. The degree of dominance of sc+ over set was increased in two lines out of five and decreased in one line. The latter indication of breakdown in the dominance level of control was not supported by results of the effect of an extra dose of sc+ in males, where all lines were similar to the unselected level.The correlated response in abdominal bristles was positive, similar in size in the three lines, and smaller than in the previous lines. The changes in abdominal score on relaxation of selection for scutellar bristles do not correlate well with the variable reductions in scutellar score across 10 relaxed lines. Positive, zero or negative genetic correlations between the two characters seem to be possible depending on the line and stage of response. In relation to abdominal scores, changes in dominance of sc+ over set occurred but were not correlated with the dominance changes for scutellar bristles. The effect of an extra dose of sc+ on abdominal bristles was similar in all six lines observed, adding 2·6-4·1 bristles, much smaller than the scutellar effect, where sc+/sc+· Y males exceeded sc+ /sc+ females. _1.1."

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Canalisation and Selection

Cited by 53 publications

References 54 publications

Differential Masking of Natural Genetic Variation by miR-9a inDrosophila

Differential Masking of Natural Genetic Variation by miR-9a inDrosophila

Synergistic epistasis between loci affecting fitness: evidence in plants and fungi

Studies on the Scutellar Bristles of Drosophila Melanogaster ID. Long-Term Selection for High Bristle Number in Three further Lines Derived From the Oregon-RC Strain, Correlated Responses in Abdominal Bristles, lUld Changes in Regulation of the Scute Locu

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